1. Field of the Invention
The present invention is broadly concerned with an improved latch mechanism of simple, compact, lightweight construction using only a minimum of parts, and which is especially designed for use with emergency deployment oxygen mask containers used in passenger aircraft. More particularly, the invention pertains to such a latch mechanism which includes cooperating, substantially axially aligned components including displaceable latch elements and an operating piston shiftable in opposite directions relative to the latch elements; the piston includes structure for positively displacing the latching elements upon piston movement in either axial direction.
2. Description of the Prior Art
A number of latch mechanism designs have been proposed for use in emergency deployment oxygen mask containers situated above or adjacent passenger seats and in other locations such as lavatories in aircraft. Such mechanisms must meet a number of rather stringent requirements. First and foremost, the latch mechanisms must operate essentially flawlessly in the event of a cabin depressurization or other incident where supplemental passenger oxygen is required. At the same time, size and weight are sometimes controlling considerations in aircraft design, and therefore the container latch mechanisms must be compact and lightweight.
A common type of latch mechanism used in this context is a pneumatic latch having a clip and an actuator, where a latch pin is squeezed into the clip and is released when enough upward force is applied to the latch pin. This mechanism relies upon the balance of force between the clip tension and the upward force on the pin. One disadvantage of this design is that the force of the door on the pin affects the force required to open the latch, and since that force is dependent on how tightly the container is packed, the opening force is inconsistent. Further, the metal clip is likely to fatigue over time, causing it to be less able to restrain the pin. Therefore, the tolerance of opening force for the latch needs to be large to account for this variability. This latch design also requires a rather large number of parts, making it heavier and more costly to produce and repair. Finally, only two operating methods can be used with this mechanism, and thus simplified deployment testing is not possible.
Another common latch mechanism employs a complicated assembly in which a short hollow column attached to the container cover door is pushed over the top of a locking mechanism where friction against two protruding balls holds the column in place. When this mechanism is actuated, a plunger core with variable thickness moves to allow the restraining balls to retract and thus no longer make contact with the locking column. The complexity of this design, with five moving parts, makes it costly to manufacture and repair. This mechanism is also relatively heavy and tall, and would not be usable in new short-height container designs. Again, there are only two opening methods with this design, pressurization and thin rod insertion. In the latter case, the design is deficient in that if the rod is inserted at an angle, it can miss the plunger altogether and/or damage the assembly.
Electrically actuated latch mechanisms have also been proposed. In one design, three jaws are locked around a latch pin. In operation, a plunger releases the jaws, with the plunger being activated by a lever controlled by a solenoid. However, this unit is relatively heavy and has only two opening methods. Another electrical design exists in which a locking ball mechanism/latch pin is employed to keep the container cover closed. This unit includes over thirty parts (including five springs), and is thus large and heavy. Latch release is indirect: a solenoid drives a spring loaded cam and shaft which pushes another spring-loaded piston back to release the three balls locking the latch pin. A manual release button associated with this unit requires a separate mechanism which also works indirectly. Another mechanism of this general type uses the same dual shaft principle to indirectly move a piston. In this design, a hook end of a lever grabs the cover and keeps it closed; if the lever is rotated, the hook releases the door. While this design does have certain advantages, it is still a parts intensive mechanism of relatively large size.
There is accordingly a real and unsatisfied need in the art for a latch mechanism usable in emergency deployment oxygen containers which is compact, lightweight, and easy to assemble using only a minimum of parts, and wherein the latch mechanism can be opened by a variety of methods.
The present invention overcomes the problems outlined above and provides a latch mechanism for releasably latching two components together. The mechanism includes a latch assembly adapted for mounting on one of the components and has a latch member with at least one latch element displaceable between a latching position and a release position, together with a piston shiftable in opposite directions relative to the latch member. The overall mechanism also has a latch pin adapted for mounting on the other of the components and normally interfitted with the displaceable latch element for releasably latching the two components together. In preferred forms, the latch member, piston and latch pin are substantially coaxially aligned, and the piston includes structure oriented to positively displace the latch element from its latching to its release position during shifting of the piston in either of its movement directions.
Preferably, the latch member is of elongated, tubular design and includes a plurality of latch elements in the form of elongated, laterally displaceable latching legs each equipped with a hook-shaped end engageable with the latch pin. Similarly, the piston has a plurality of elongated slots with each of the legs received within a corresponding slot. The piston and displaceable legs have cooperating surfaces so that, upon movement of the piston in either axial direction, the latching legs are displaced laterally so as to effect delatching.
The latch mechanism is normally operated pneumatically, although in alternative designs, various operating mechanisms can be adopted. These would include electrical, mechanical, electromagnetic or chemical means for shifting of the mechanism piston. Hence, the preferred pneumatic/diaphragm operating mechanism could readily be replaced by a number of other operationally equivalent systems such as a solenoid mechanism. Further, the design permits a number of other opening methods, such as by pushing or pulling the piston by appropriate rod manipulations.